Circular stapling instruments are well known in the surgical art for bowel surgery. An example of such a device is the Endopath ILS ECS 25 Endoscopic Curved Intraluminal Stapler made by Ethicon Endo Surgery Inc. Many circular stapler patents exist, for example U.S. Pat. No. 4,207,898 to Becht, U.S. Pat. No. 4,351,466 to Noiles, U.S. Pat. No. 5,292,053 to Bilotti et al., and U.S. Pat. No. 5,344,059 to Green et. al.
Circular stapling instruments require proper alignment between the staple cartridge assembly and the anvil in order to form high-quality staples. Typically, circular stapling instruments attempt to do this by aligning splines on the anvil with keyways on the casing, and by aligning the staple driver to the casing. In such manner, by aligning the anvil and the casing, and by aligning the staple driver to the casing, the anvil is aligned with the staple driver through their separate alignments with the casing. However, by requiring the alignment of the anvil and the casing, and the alignment of the staple driver to the casing, in order to achieve alignment of the anvil with the staple driver, increased alignment variation may result.
A circular stapling instrument is needed which provides proper alignment between the anvil and the staple driver without requiring alignment between both the anvil and the casing, and the staple driver and the casing, in order to decrease the potential of alignment variation.